Bekko tombo (Libellula angelina)
Classified as Critically Endangered (CR) on the IUCN Red List 2006 (1).
The bekko tombo is a stunning golden to rusty-brown dragonfly (2) adorned with a dark stripe down the centre of the abdomen and a distinctive pattern of dark markings on its wings. Like other members of the Libellulidae family, this dragonfly has a relatively short, broad abdomen, and its body is distinctly shorter than its wingspan (3).
The bekko tombo occurs in China (central and north), Japan (Honshu, Shikoku, Kyushu and offshore islands) and Korea (1).
Found in old, stable ponds in lowland hill areas, with vegetation such as reeds emerging from the water, although an area of clear, open water is also required (1) (2). Larvae usually crawl around in the bottom sediments (2).
Dragonflies (Odonata) start their life as aquatic larvae or nymphs, passing through a series of developmental stages or ‘stadia’, and undergoing several moults as they grow. Before the final moult (emergence), metamorphosis occurs in which the larvae transform into the adult form (4). The bekko tombo has a larval period of a year, with eggs hatching from May to June, and adults emerging the following spring (2). After emergence, adults undergo a pre-reproductive phase known as the maturation period, which is when individuals normally develop their full adult colour. Odonata usually feed on flying insects and are generalised, opportunistic feeders, often congregating around abundant prey sources such as swarms of termites or near beehives (4).
There is often fierce competition between males for access to reproductive females, and females typically begin to lay eggs in water immediately after copulation, often guarded by their mate. However, females of some species can store live sperm in their body for a number of days (4).
Once relatively abundant, bekko tombo populations have undergone drastic declines in recent decades as a result of habitat destruction and degradation and introduced predators. Ponds have been filled to allow urban expansion, or in some urban areas, ponds have been made into artificial ponds with concrete banks, which may be unsuitable for this species. Likewise, grassy fields, which females and immature males rely upon for refuges, have greatly diminished in recent years (1). Introduced alien species, such as Procambarus clarkii (Crustacea), Micropterus salmoides (carnivorous fish), and Myocastor coypus (a large, semi-aquatic rodent), have also contributed to the dragonfly’s demise either through direct predation, or through feeding on the water plants that sustain this native species (1) (5). Sadly, the pattern of decline is only expected to continue (1).
Considered a national natural treasure in Japan (5), the bekko tombo became protected by the Japanese Ministry of Environment in 1993, and collection is prohibited by law (1). Nevertheless, this does little to protect the dragonfly’s disappearing habitat (1). Thus, some NGOs have begun to conserve this insect and its habitat at specific pond sites, for example at Okegaya, Imuta, Misumi and Noyori-shin ponds (1) (6). At Misumi Pond, the Oita Dragonfly Society is feeding and breeding the larvae of bekko tombo to help restore the diminished population, with 149 larvae successfully hatching in spring 2005 in tanks installed in the pond. The Oita Dragonfly Society is also observing the mating and egg-laying behaviour of females, with the hope that the information gained will help them in their breeding scheme (6). Thus, despite an ongoing decline, national pride in this native dragonfly provides an element of hope for its future, in Japan at least, through inspiring concerted conservation efforts by dedicated individuals and organisations such as the Oita Dragonfly Society.
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- Metamorphosis: an abrupt physical change from the larval to the adult form.
- NGO: Non-Governmental Organisations.
IUCN Red List (December, 2009)